Question

In a common emitter transistor amplifier circuit, the current gain \(\alpha=0.8\). If the base current changes by \(3 \mu \mathrm{~A}\) then the collector current changes by

• A. \(4\mu \text{ }\mathrm{A}\)
• B. \(12\mu \text{ }\mathrm{A}\)
• C. \(6\mu \text{ }\mathrm{A}\)
• D. \(24\mu \text{ }\mathrm{A}\)

Hint:

Convert alpha to beta using beta = alpha/(1 - alpha), then multiply by the base current change.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept
The current gain in common emitter mode is \(\beta=\dfrac{\Delta I_C}{\Delta I_B}\) and \(\beta=\dfrac{\alpha}{1-\alpha}\).

Step 2: Find beta
\(\beta=\dfrac{0.8}{1-0.8}=4\).

Step 3: Calculation
\(\Delta I_C=\beta\,\Delta I_B=4\times3\ \mu\text{A}=12\ \mu\text{A}\).

Final Answer:
The collector current changes by 12 microamperes. \[ \boxed{\text{(B) }12\mu\text{ A}} \]